Anxiety about Supervisor's Reaction

My supervisor was away the last few days and I had a coworker ask me if I could find anything division wise regarding ordering books on a specific, sensitive topic. I reached out to a higher up who is responsible for all of us librarians at a division level as I wanted to do my best to get an answer for my coworker.

My supervisor is back today and I'm worried she is going to react poorly to my not waiting until her return to ask her. She has a history of volatile and unprofessional outbursts when she feels she has been "worked around" or not given her due respect.

I am anxious she is going to explode at me (again as she's done this a few times before) even though I had the best of intentions. :(